Crack the 4 eggs into a bowl, add ½ teaspoon mustard and salt to taste, and whisk until the mixture is uniform and slightly frothy.

Place a non-stick pan over medium heat and add 2 tablespoons butter. Melt the butter, watching carefully so it melts but does not brown.

As soon as the butter is melted (and not browned), pour the whisked eggs into the pan and immediately reduce the heat to low.

Let the eggs sit undisturbed for about 20 seconds so they begin to set on the bottom.

Using a wooden spoon or spatula, gently stir by lifting and folding the eggs from the bottom of the pan; break up any large curds as you go.

Continue lifting, folding, and gently stirring until the eggs are softly set and still slightly runny in places. Take your time and keep the heat low.

Remove the pan from the heat just before the eggs look fully cooked—the residual heat will finish them.

Give the eggs one last gentle stir, then serve immediately.